A CFD study on the correlation between the skew angle and blade number of hydrodynamic performance of a submarine propeller

Noise generated by ships is one of the most significant noises in seas, and the propeller has a significant impact on the noise of ships, which reducing it can significantly lower the noise of vessels. In this study, a genetic algorithm was used to optimize the hydro-acoustic and hydrodynamic performance of propellers. The main objectives of this optimization were to reduce the propeller noise and increase its hydrodynamic efficiency. Modifying the propeller geometry is one of the most effective methods for optimizing a propeller performance. One of the numerical methods for calculating propeller noise is the Ffowcs Williams and Hawkings (FW-H) Model. A numerical code was developed by authors which solved these equations using the velocity and pressure distribution around the propeller and calculated its noise. To obtain flow quantities and to investigate the hydrodynamic performance of the propeller, a code was developed using a Boundary Element Method, the panel method. The geometry of DTMB 4119 propeller was selected for optimization, where geometric modifications included skew angle, rake angle, pitch to diameter (P/D) distribution, and chord to diameter (c/D) distribution. Finally, the results of geometric optimization were presented as Pareto optimal solutions. The results indicated that the optimum geometries had rake angles between 8.14 and 12.05 degrees and skew angles between 31.52 and 39.74 degrees. It was also observed that the increase in the chord up to a specific limit enhanced the efficiency and reduced the noise of the propeller.

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Method to Control Unsteady Force of Submarine Propeller Based on the Control of Horseshoe Vortex

Journal of Ship Research ◽

10.5957/jsr.2012.56.1.12 ◽

2012 ◽

Vol 56 (01) ◽

pp. 12-22

Author(s):

Liu Zhihua ◽

Xiong Ying ◽

Tu Chengxu

Keyword(s):

Hydrodynamic Force ◽

Horseshoe Vortex ◽

Wake Vortex ◽

Noise Performance ◽

Skew Angle ◽

Vortex Control ◽

Blade Number ◽

Unsteady Force ◽

Vortex Control Baffler ◽

Circumferential Nonuniformity

The submarine propeller works in the submarine wake with severe circumferential nonuniformity, which causes the hydrodynamic force to act on the blade. This results in severe oscillation with the rotation of the propeller and impairs the hydrodynamics and noise performance of the submarine propeller. The horseshoe vortex generated at the hull-appendages junctions of the submarine has important influence on wake uniformity. In the present study, the state of the submarine horseshoe vortex is analyzed and a new method of vortex control baffler is presented. The aim is to weaken the horseshoe vortex. Based on the wind tunnel experiment and numerical simulation on the submarine model, the vortex control baffler can decrease the strength of the submarine horseshoe vortex and improve the uniformity of the submarine wake. Vortex control bafflers adapted for the fully appended SUBOFF model are designed, and the unsteady force of three kinds of propellers functioned after the SUBOFF model is calculated numerically. The results show that although the skew angle and blade number are different, the amplitudes of the unsteady force acting on the blades of all three propellers decreased by 50% to 80% due to the effects of the vortex control baffler.

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Numerical Study of the Effect of Propellers Skew on Cavitation Performance

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.705.405 ◽

2013 ◽

Vol 705 ◽

pp. 405-409

Author(s):

Zhi Feng Zhu

Keyword(s):

Bubble Dynamics ◽

Volume Fraction ◽

Numerical Study ◽

Tip Vortex ◽

Hydrodynamic Performance ◽

Navier Stokes ◽

Skew Angle ◽

Cavitation Performance ◽

Numerical Predictions ◽

Hybrid Grid

The effect of propeller skew on cavitation distribution, thrust and the torque is studied numerically. With the hybrid grid strategy and the sliding mesh, the Unsteady Navier-Stokes (N-S) and the Bubble Dynamics equations were solved to predict the vapor volume fraction around ships propellers blades. The numerical predictions of the sheet and the tip vortex cavitation of the propeller E779A are in agreement with the results in other literature in general. For propeller models DTMB, the proper increase of the propeller skew angle may enhance the hydrodynamic performance.

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A computational investigation of noise spectrum due to cavitating and non-cavitating propellers

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090219892368 ◽

2019 ◽

Vol 234 (2) ◽

pp. 374-387

Author(s):

Savas Sezen ◽

Sakir Bal

Keyword(s):

Near Field ◽

Noise Spectrum ◽

Research Field ◽

Hydrodynamic Performance ◽

Navier Stokes ◽

Marine Propellers ◽

Sheet Cavitation ◽

Blade Number ◽

Numerical Studies ◽

Propeller Blades

In this article, noise spectrum of marine propellers is investigated in uniform flow under non-cavitating and cavitating conditions. New results are presented for this research field. Hydrodynamic performance of both non-cavitating and cavitating marine propellers is first analyzed by viscous and potential based flow solvers. In viscous solver, sheet cavitation on propeller blades is simulated with Schnerr–Sauer cavitation model based on Rayleigh Plesset equation using volume of fluid approach. Numerical hydrodynamic results based on viscous solver is compared with potential solver and then validated with experimental data of benchmark David Taylor Model Basin 4119 model propeller. Later, noise spectrum of model propellers is predicted by a hybrid method which combines Reynolds-averaged Navier Stokes and Ffowcs Williams Hawkings equations. Computed noise spectrum is compared with other numerical studies in the literature for the selected model propeller. In addition, hydrodynamic and hydroacoustic pressures are compared in near field to show reliability of numerical solution. Effects of blade number on hydrodynamic performance and noise spectrum are also investigated. Numerical results indicated that as blade number increases, propeller noise level decreases for different loading conditions due to decreased blade loading (circulation) per blade. However, propeller efficiency increases as blade number decreases.

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Numerical analysis on effects of blade number on hydrodynamic performance of low-pitch marine cycloidal propeller

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090219876508 ◽

2019 ◽

Vol 234 (2) ◽

pp. 490-501

Author(s):

Mohammad Bakhtiari ◽

Hassan Ghassemi

Keyword(s):

Numerical Method ◽

Stokes Equations ◽

Thrust Force ◽

Circular Disk ◽

Hydrodynamic Performance ◽

Navier Stokes ◽

Thrust Coefficient ◽

Navier Stokes Equations ◽

Blade Number ◽

Marine Propulsion

Marine cycloidal propeller, as a special type of marine propulsion system, is used for ships that require high maneuverability, such as tugs and ferries. In a marine cycloidal propeller, the thrust force is generated by rotation of a circular disk with a number of lifting blades fitted on the periphery of the disk, so that the propeller axis of rotation is perpendicular to the direction of thrust force. Each blade pitches about its own axis, and the thrust magnitude and direction can be adjusted by controlling the pitching angle of the blades. Therefore, the propulsion and maneuvering units are combined together and no separate rudder is needed to maneuver the ship. Two configurations of marine cycloidal propeller have been studied and developed based on propeller pitch: low-pitch propeller (designed for advance coefficient less than one, means λ < 1) and high-pitch propeller (designed for λ > 1). Low-pitch marine cycloidal propellers are used in applications with low-speed maneuvering requirements, such as tugboats and minesweepers. In this study, the effects of blade number on hydrodynamic performance of low-pitch marine cycloidal propeller with pure cycloidal motion of the blades are investigated. The turbulent flow around marine cycloidal propeller is solved using a 2.5D numerical method based on unsteady Reynolds-averaged Navier–Stokes equations with shear-stress transport k–ω turbulent model. The presented numerical method was validated against experimental data and showed good agreement. The results showed that the thrust coefficient of marine cycloidal propeller generally decreases by increasing the blade number, whereas the torque coefficient increases. Consequently, the hydrodynamic efficiency of marine cycloidal propeller drops as the blade number increases.

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